Since it's intermittent, test the voltage to the solenoid sometime when the trailer brakes are locked up, and another time when they're working (not locked up). Have someone else just hold the brake pedal down in the truck so you can keep it in reverse and test the voltage to the solenoid. Does your trailer harness have a 5 prong connection between the truck/trailer? The idea behind the solenoid is that when the truck is put into reverse, it sends voltage through that 5th wire that activates the solenoid and locks the brakes out from engaging. If you have no other wiring issues, it sounds like a bad solenoid to me... but I'm new at this trailer brake thing, so I don't know that I'm qualified to answer all of these questions haha.

Also, does your trailer have any reverse lights on it? Are those lit up when the brakes are locked up? If the reverse lights on the trailer come on, but the brakes are still locked up, that would also point to a bad solenoid. If the brakes lock up, and the reverse lights are also off, that would point to some sort of wiring issue that isn't transferring current to that 5th wire. Just another thing to check.

Great advice. So far there has been a direct correlation between no reverse lights on the trailer and locking up. Sounding likely a wiring issue.

Is there any corrosion between the wiring harness of the truck and the harness of the trailer? Maybe spray some electrical cleaner on both sides of the plug. Also check the back side of the plug on the truck side, and make sure none of the connections are loose from pushing the trailer harness into them.

Is there any corrosion between the wiring harness of the truck and the harness of the trailer? Maybe spray some electrical cleaner on both sides of the plug. Also check the back side of the plug on the truck side, and make sure none of the connections are loose from pushing the trailer harness into them.

I will spray some electrical cleaner. Good idea.

I have tested the plug on the truck side with a volt meter and had good power / connection

Next time the brakes lock up, try to test the solenoid (if you can reach it). That will at least give you an idea where the problem is occuring. If no voltage at the solenoid, then the problem lies in the wire between there and the truck.

Next time the brakes lock up, try to test the solenoid (if you can reach it). That will at least give you an idea where the problem is occuring. If no voltage at the solenoid, then the problem lies in the wire between there and the truck.

How's the ground connection look?

When I checked last time, all the wires (ground included), looked good. However, I am going to hook and try again when I get home tonight and see if I can recreate.

Is there any corrosion between the wiring harness of the truck and the harness of the trailer? Maybe spray some electrical cleaner on both sides of the plug. Also check the back side of the plug on the truck side, and make sure none of the connections are loose from pushing the trailer harness into them.

I will spray some electrical cleaner. Good idea.

I have tested the plug on the truck side with a volt meter and had good power / connection

I cleaned all the contact points in plug with spray cleaner. I disassembled the trailer plug and tightened the center pin (back up lights). I checked the actuator ground wire (in good condition). I did not see an obvious place to test power to actuator; however I tested the system at this point and was able to deactivate breaks 12x in a row (back up lights on trailer do NOT come on when brakes are NOT deactivated. Putting my bet on an electrical problem).

We are traveling 4 hours to eastern Washington on Wednesday / Memorial weekend. This will be the big test that I corrected the problem.

I have an appointment at the trailer repair place for Wednesday next week if the problem persists in any manner.

It could be your relay in your truck, there is a relay activating the backup portion on your 7 pin connector. The relay on mine was under the hood. Just a thought for something else to check. You should be able to check the center post on your truck, put in reverse not running with key on and use test light to see if you are getting power.

if you look at your manual it will show you where the relay is located

It could be your relay in your truck, there is a relay activating the backup portion on your 7 pin connector. The relay on mine was under the hood. Just a thought for something else to check. You should be able to check the center post on your truck, put in reverse not running with key on and use test light to see if you are getting power.

I checked the relay and it is in good shape. I also tested the center post on the truck side and I am getting appropriate power.

Pulling my boat home this weekend, i noticed the trailer brakes "surging and jumping" when I slowed down to a stop. Any thoughts about what might be going on here?

Also, on occasion, when trying to back up, the brake lock-out doesn't activate causing the trailer to lock up. Not sure if this is related or not.

Thank you in advance.

If you still have the "surging and jumping" problem, it could be due to warped rotors. I had the same problem about 10 years ago with an almost brand new dual axle trailer. It turned out to be a badly warped rotor. It may have been defective to begin with, or warped from being dunked in the lake when the rotor was hot. Replaced the rotor and the problem went away. The problem was much worse when the trailer was empty than with the boat on it.